1. Kursk State Medical University
Normal Physiology Department
Regulation Of Kidney
∙Methods and Determination of Kidney
Function
Hess Amanda B.
Repalova Natalya V.
Kursk 2012 Group 20
2. Plan
• Autoregulation of the kidneys
o (Tubuloglomerular feedback, glomerulotubular balance, pressure diuresis)
• Role of kidneys in regulation of osmolarity and
volume
• Renal sodium regulation
• Renal potassium regulation
• Renal calcium regulation
• Methods for studying renal function
o (Tubular fluid-to-plasma concentration, determination of the renal blood
volume, dilution test, micro-puncture, microperfusion, patch-clamp
method, determination of clearance, insulin clearance, creatinin
clearance, Zimnitsky’s test, concentration test)
3. Autoregulation Of The
Kidneys
• Includes 3 components:
1) Tubuloglomerular Feedback
2) Glomerulotubular Balance
3) Pressure Diuresis
4. 1) Tubuloglomerular Feedback
• Has 3 components:
afferent arteriole, efferent
arteriole and macula
densa.
• The macula densa cells
sense the changes in the
volume of delivery to the
distal tubule. Decrease in
NaCl concetration initiates
a signal from the macula
densa cell what has two
effects: 1- it increases renin
release from the
juxtaglomerular cells of
afferent and efferent
arterioles. 2- it decreases
resistance of the afferent
arterioles (dilation).
5. • Renin: enzyme, which
catalyses the destruction
of angiotensin (plasma
protein produced in the
liver) into angiotensin I
(catalysed by converting
enzyme to form
(glomerular filtration
rate)
angiotensin II).
• Effects of Angiotensin II:
o Stimulates aldosterone secretion
o Constrict the arterioles and ↑
arterial pressure
o Stimulates Na+
reabsorption, mainly in the
proximal tubulles
o Constrict efferent arterioles
o Facilitates release of ADH
o ↑ thirst
o Facilitates release of
prostaglandins
6. 2) Glomerulotubular Balance
• Is the intrisic ability of the
tubules to increase their
reabsorption rate in
response to increased
tubular inflow.
• (The balance between
reabsorption of solutes in
the proximal renal tubules
and glomerular
filtration, which must be as
constant as possible. If the
glomerular filtration rate rises
or falls, the rate of tubular
reabsorption must rise or fall
proportionally. Balance is
maintained by
neural, hormonal, and other
mechanisms).
7. 3) Pressure Diuresis
• Is a phenomena which shows that even a
small increase in arterial pressure often causes
marked increase in urinary excretion of Na+
and water.
• (increased urinary excretion of water when
arterial pressure increases, a compensatory
mechanism to maintain blood pressure within
the normal range).
8. Role of the Kidneys in Regulation
of Osmolarity and Volume
• Kidney excretes excess
water in hyperhydrationin
the form of dilute urine or
save water in dehydration
by excreting concentrated
urine.
• Central osmoreceptors
(hypothalamus) and
peripheral osmoreceptors
(kidneys, liver, spleen and
blood vessels) sense
changes in blood osmolarity
and send information to the
hypothalamus, which
regulates the concentration
of ADH in the blood.
9. • Also volume receptors
in blood vessels and
the left atrium
baroreceptors send
impulses to the CNS to
regulate the volume of
blood.
• ADH increases the
water permability of
the distal
tubules, collecting
tubules and collecting
ducts. More water is
retained in the body to
help stabilize the
extracellular volume.
10. Renal Sodium Regulation
• Na+ excreted= Na+filtered –
Na+ reabsorbed
• The low total body Na+:
causes low
cardiovascular
pressure, which from
venous, atrial, arterial
baroreceptors, initiates
reflexes that:
o 1) restore the cardiovascular
pressure (from direct action on
the cardiovascular system – SNS)
o 2) lower GFR (glomerular filtrate
rate) and increase Na+ • Stimulates Na+/K+ active
reabsorption (aldosterone). transport in the basement
membrane
• Aldosterone: stimulates the • Stimulates Na+ reabsorption (and
production of proteins that secretion of K+) in the
function as Na+ channels in the
intestine, sweat glands, salivary
luminal membrane.
glands.
13. Methods Studying Renal Function
• Tubular Fluid-to-Plasma
concentration (TF/P)
o TFosm/Posm=1 (tubular fluid is
isosmotic with respect to
plasma)
o TFosm/Posm<1 (tubular fluid is
hyposmotic with respect to
plasma)
o TFosm/Posm>1 (tubular fluid is
hyperosmotic with respect to
plasma)
• (collect fluid inside and outside
of nephron with micropipete
and compare).
14. Determination of the Renal
Blood Volume
• Indirect method for • 1)insert PAH in the blood
measuring the secreting
capacity of the renal • 2)check the
tubular cells (renal plasma [PAH], collected from
flow). blood
• PAH (para aminohippuric
acid) is secreted by cells of
renal tubules, if PAH is • 3)after pass through
present in arterial blood in
kidney, collect the blood
low [], blood is completely
again and check the
free from PAH after passes
[PAH].
through kidney.
• If blood has a low
[PAH], means that kidney
has a good flow and
function.
15. Dilution Test
• This method is used to • Test is hold for 12 hours.
examination of dilution
and excretion abilities of
the kidneys. • The patients drinks 1,5L
• Normal kidney function: of water.
great part of the drunk
fluid will be excreted
during first 4 hours • During next 4 hours,
(density of urea: 1,002 – volume and density of
1,001).
urea are determined
• During next 8
hours, portions of urea each 30 minutes, and
decrease gradually in during next 8 hours,
volume and becomes each 2 hours.
normal by the end of the
test.
16. Concentration Test
• This method is used to
examination of
concentration and
excretion abilities of the • The patient is not
kidney. allowed to take fluid
during 12 hours and
• Normal kidney every 2 hours the
concentration: volume volume and density of
of urea will be greatly urea is determined.
decreased (up to
100ml and less) and
density will be
increased (up to 1,030)
17. Micro-Puncture Test
• Microfusion of separate
renal tubules plays an
important role in studying
the formation of urine.
• Main idea: fluid was
derived from glomerular
capsule with a
micropipete by Richard in
1st time.
• How changes the
concentration of urine in
each part of neprhon.
(Not destroys the nephron)
18. Microperfusion
• 1st: insert concrate
(A) (A’)
substance (A)
• 2nd: collection of fluid
before the 2nd
block/vent (A’)
• [A]→[A’]
- How change the
concentration?
- -Present or not reabsorption?
19. Patch-Clamp Method
• Used to study the role
of each nephron part
in urine production and
the mechanism of
transport of substance
in tubular cell
membrane.
- (How much ion
diffusion per unit of time?)
20. Determination of CFR (glomerular
filtration rate - clearance)
• Clearance: measure of • Glomerular filtration rate
the volume of plasma (GFR) is the volume of
completely free of a fluid filtered from the
given substance per renal (kidney) glomerular
unit. capillaries into the
Bowman’s capsule per
• Renal Clearance of a unit time. Central to the
given substance is a physiologic maintenance
ratio of the renal of GFR is the differential
excretion of the basal tone of the afferent
substance to its and efferent arterioles.
concentration in the
blood plasma.
(unit: ml/min)
21. Insulin Clearance
• Fructo-polysacharide is
used for determining
renal filtration.
• Insulin: only filtered, not • Cx/Cins=1 (only filtered)
absorbed or secreted
(does not combine with
plasma protein). • Cx/Cins<1 (filtrated and
• Since insulin is neither reabsorpted)
reabsorbed nor secreted
by the kidney after • Cx/Cins>1 (filtrated and
glomerular filtration, its
rate of excretion is secreted)
directly proportional to
the rate of filtration of
water and solutes across
the glomerular filter.
22. Creatinin Clearance
• One method of • Normal range: 80-
determining GFR 110mL/min (plasma)
(glomerula filtration per 1,73m of body
rate) from creatinine is surface area.
to collect urine (usually • Plasma (creatinin)
for 24 hours) to remains constant
through life (0,8-
determine the amount 1mg/dL)
of creatinine that was
• Creatinin is produced
removed from the by muscle
blood over a given metabolism, and
time interval. decrease with age
(muscle ↓ action =
nephrons ↓ activity)
23. Zimnitsky’s Test (clinical test for
kidneys)
• At 6 am the patient • Zimnitsky's test based
empties his bladder, on a study of the
untill 6 am of the next relative density of
day, he collects urea in individual urine emitted
8 pots. (limit 1,5L/day) during random
• Normal result: urination during the
common amount of day in a certain
urea daily is 1-2L. rhythm. The study was
o Density of urea: 0,010 – 1,025 conducted in the
(such changes during the day are normal feeding regime
normal – reaction of the kidneys
on changing water/food regimen without loss of fluid.
along all day)
24. THANK YOU FOR YOUR ATTENTION!!
Thank You For Your
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